Co-flow diffusion flame burner device used for fabricating an optical waveguide

ABSTRACT

The present invention provides a co-flow diffusion flame bunier for use in fabricating an optical waveguide, which includes a source material gas injection tube, through which a fuel gas, a source material to be mixed with the fuel gas, and a dilution gas to control the temperature of the flame generated by the combustion of the fuel gas are injected; a shield gas injection tube, disposed coaxially with the source material gas injection tube at the exterior of the source material gas injection tube and through which a shield gas is injected to prevent the particles produced by the combustion reaction of the fuel gas and an oxidation gas from sticking to the end of the source material gas injection tube; and, an oxidation gas injection tube, disposed coaxially with the shield gas injection tube at the exterior of the shield gas injection tube and through which an oxidation gas is injected to react with the fuel gas.

CLAIM OF PRIORITY

[0001] This application makes reference to and claims all benefits accruing under 35 U.S.C. Section 119 from an application entitled “CO-FLOW DIFFUSION FLAME BURNER DEVICE FOR FABRICATING OF AN OPTICAL WAVEGUIDE,” filed in the Korean Industrial Property Office on Sep. 5, 2000, and there duly assigned Ser. No. 00-52473.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a device for fabricating an optical waveguide, and, more particularly, to a co-flow diffusion flame burner device that is used in fabricating an optical waveguide.

[0004] 2. Description of the Related Art

[0005] Generally, an optical waveguide, which is widely used as an optical signal transmission medium in optical communication systems, is fabricated by depositing source material, such as SiO₂, GeO₂, P₂O₅ or B₂O₃, on a silicone substrate, tube, etc. There are axial deposition method, flame hydrolysis deposition, etc.

[0006] In particular, the flame hydrolysis deposition method is specifically used in fabricating an optical waveguide. It involves depositing glass material on the silicon substrate by a means of oxy/hydrogen flame that is generated from a co-flow diffusion flame burner.

[0007]FIG. 1 is a schematic view illustrating the procedures for forming an optical waveguide thin layer on a substrate using the conventional flame hydrolysis deposition method. As shown in FIG. 1, the source material undergoes hydrolysis and oxidation while passing through the oxy/hydrogen flame that is generated by the co-flow diffusion flame burner device 1 to form fine particles known as “glass soot”.

[0008] The “glass shoots” are coagulated when the particles collide as they travel through the flame, then deposited on the silicon substrate 10 by thermophoresis. At this point, by controlling the composition ratio of the source material, the thin layers, including an undercladding layer 20, a core layer 30 and an overcladding layer (not shown), are formed one after another, as shown in FIG. 1.

[0009] The deposition steps maybe carried out by disposing several sheets of silicon substrate 10 on a rotating turntable while traversing the co-flow diffusion flame burner device 1 (indicated by M₁), or by reciprocally moving the co-flow diffusion flame burner device 1 along the two-dimensional line (indicated by M₂) while the silicon substrate 10 is stationary.

[0010]FIG. 2 is a perspective view of the co-flow diffusion flame burner according to the prior art system. As shown in FIG. 2, the co-flow diffusion flame burner 100 according to the prior art consists of an injection tube for source material/carrier gas 110 with a plurality of tubes arranged co-axially, an injection tube for fuel/dilution gas 120, and an injection tube for oxidation gas 130.

[0011] The injection tube for source material/carrier gas 110 is used for injecting the source material S and carrier gas gc, which is used for bubbling the source material. The source materials used are, for example, SiCl₄, GeCl₄, POCl₃, and BCl₃. Most of these materials, except BCl₃, are in a liquid state at room temperature. Therefore, the source materials must be bubbled through the carrier gas, gc. The carrier gas, gc, are, for the formation of bubbles, He, Ar, and N₂, for example.

[0012] The injection tube for fuel/dilution gas 120 is used for injecting the fuel gas to generate flame and the dilution gas, g_(d), to control the temperature of the flame. As the fuel gas H₂ is used, the dilution gas, He, Ar, and the like—such as those that can be diluted in hydrogen—are used.

[0013] The injection tube for oxidation gas 130 is used for injecting the oxidation gas g_(o) to generate the flame by a combustion reaction with the fuel gas, g_(f). Here, O₂ may be used as the oxidation gas, g_(o).

[0014] Meanwhile, in the fabrication of the optical waveguide according to the conventional flame hydrolysis deposition method, it is very important that thin layers to be formed over the silicon substrate have a uniform composition and thickness in order to provide an optical waveguide with excellent optical transmission properties. The formation of such thin layers can be accomplished by realizing a uniform particle size distribution as well as a uniform composition and number concentration distribution of the glass soot that are produced from the co-flow diffusion flame burner 100.

[0015] However, the conventional diffusion flame burner 100 exhibits a Gaussian type concentration distribution of source material in which the concentration is high at the center of the burner device and is gradually lowered away from the center. Therefore, the composition of the glass soots forming the thin layers on the silicon substrate varies with the distance from the center and thus is difficult to form uniformly thin layers.

[0016] Furthermore, it is necessary that the source material travel a certain distance from the injection nozzle end of the flame burner before forming the glass soot. The traveling distance needed to form the particles is increased when the flux of the source material is higher. That is, in the conventional co-flow diffusion flame burner 100, the concentration of the source material varies radially from the center portion, thus leading to a variation in the time required to form particles and the coagulation. Such variation consequently leads to variations in the particle size of the glass soot. Thus, the distribution of the size of the particles is close to a log normal distribution. In addition, an increase in the particle size and non-uniformity of the distribution of the particle size may cause problems during the sintering process, which is followed by the deposition process in fabricating an optical waveguide.

SUMMARY OF THE INVENTION

[0017] The present invention is related to a co-flow diffusion flame burner for use in fabricating an optical waveguide, by producing glass soot with a reduced particle size and a uniform distribution of the particle size.

[0018] Another aspect of the present invention is to provide a co-flow diffusion flame burner for use in fabricating an optical waveguide and that is capable of uniformly depositing the glass soot over a predetermined broad area.

[0019] In another aspect, the present invention consists of a co-flow diffusion flame burner for use in fabricating an optical waveguide and includes a source material gas injection tube, through which a fuel gas, a source material to be mixed with the fuel gas, and a dilution gas to control the temperature of the flame, which is generated by the combustion of the fuel gas, are injected; an shield gas injection tube, disposed coaxially with the source material gas injection tube at the exterior of the source material gas injection tube and through which a shield gas is injected to prevent the particles produced by the combustion reaction of the fuel gas and an oxidation gas from sticking to the end of the injection tube; and, an oxidation gas injection tube, disposed coaxially with the shield gas injection tube at the exterior of the shield gas injection tube and through which an oxidation gas is injected to react with the fuel gas.

[0020] Another aspect of the present invention is directed to a process for fabricating an optical waveguide using a co-flow diffusion flame burner and includes the steps of: introducing a fuel gas with a source material or a dilution gas into one end of the diffusion flame burner; introducing an oxidation gas into the one end of the diffusion flame burner; generating a flame at the one end of the diffusion flame burner where the fuel gas and the oxidation gas impinge; and, simultaneously introducing an inert gas to the one end of the diffusion flame burner to prevent the particles produced by the combustion of the fuel gas from sticking to the one end of the diffusion flame burner.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The above advantages of the present invention will become more apparent by describing in detail preferred embodiments thereof with reference to the attached drawings in which:

[0022]FIG. 1 is a schematic view illustrating the procedure according to a conventional art system for forming thin layers of the optical waveguide on a substrate by the flame hydrolysis deposition method;

[0023]FIG. 2 is a perspective view illustrating the conventional co-flow diffusion flame burner;

[0024]FIG. 3 is a perspective view illustrating a co-flow diffusion flame burner device according to a first preferred embodiment of the present invention; and,

[0025]FIG. 4 is a perspective view illustrating a co-flow diffusion flame burner device according to a second preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0026] In the following description, for purposes of explanation rather than limitation, specific details are set forth such as the particular architecture, interfaces, techniques, etc., in order to provide a thorough understanding of the present invention. For purposes of simplicity and clarity, detailed descriptions of well-known devices, circuits, and methods are omitted so as not to obscure the description of the present invention with unnecessary detail.

[0027]FIG. 3 is a perspective view illustrating a co-flow diffusion flame burner 200 according to the first preferred embodiment of the present invention. As shown in FIG. 3, the co-flow diffusion flame burner device 200 comprises a source material gas injection tube 210, a shield gas injection tube 220, and an oxidation gas injection tube 230.

[0028] Now, a detailed description will be made regarding this invention with reference to the drawings.

[0029] 1. Source material gas injection tube 210

[0030] The source material gas injection tube 210 is used for injecting a fuel gas g_(f), a source material S that is to be mixed with the fuel gas g_(f), and a dilution gas g_(d) to control the temperature of the flame, which is generated by the combustion of the fuel gas g_(f). The source materials for the formation of glass soots are, for example, SiCl₄, GeCl₄, POCl₃, and BCl₃. Also, as for the dilution gas, He, Ar, N₂, and other gas that may be diluted in hydrogen, are used. The feeding rate of the fuel gas g_(f) and the source material S are selectively controlled by a mass flow controller (not shown).

[0031] Prior to mixing the fuel gas g_(f) and/or the dilution gas g_(d), the source material S is supplied to a bubbler, to which the fuel gas g_(f) and/or the dilution gas g_(d) is passed through. Thus, in the present invention, the source material S is not transferred by a specific carrier gas as in the prior art system. Rather, the source material S is bubbled with the fuel gas g_(f) and/or the dilution gas g_(d) and injected in a vapor phase through the source material gas injection tube 210 of the co-flow diffusion flame burner 200. As a result, the spot where the source material is injected and the spot where the flame is generated by the combustion of the fuel gas g_(f) are same. Hence, the glass soots are formed at the same time the combustion of the fuel gas g_(f) occurs.

[0032] Furthermore, since the hydrogen, which is used as the fuel gas g_(f), has a diffusion coefficient greater than those of the carrier gases which are used for transferring the source material in the prior art, the glass soot can be formed over the broader area in a short period of time. Therefore, the distribution of the glass soot within the flame is uniform and the coagulation effect of the particles is reduced, causing a reduction in the size of the particles. Such uniform distribution and reduction in the particle size enable the sintering process to be favorably carried out after the deposition process.

[0033] 2. Shield gas injection tube 220

[0034] The shield gas injection tube 220 is disposed coaxially with the source material gas injection tube 210 at the exterior of the source material gas injection tube 210. This arrangement allows the injection of a shield gas g_(s) to prevent the particles produced by the combustion of the fuel gas g_(f) from sticking to the end of the injection tube 210. As the shield gas g_(s), a small amount of an inert gas may be used.

[0035] 3. Oxidation gas injection tube 230

[0036] The oxidation gas injection tube 230 is disposed coaxially with the shield material gas injection tube 220 at the exterior of the shield gas injection tube 220. This arrangement allows the injection of an oxidation gas g_(o) to react with the fuel gas g_(f). Here, oxygen may be used as the oxidation gas g_(o).

[0037]FIG. 4 is a perspective view illustrating a co-flow diffusion flame burner 300 according to the second preferred embodiment of the present invention. As shown in FIG. 4, the co-flow diffusion flame burner device 300 includes a first source material gas injection tube 310; a first shield gas injection tube 320; a first oxidation gas injection tube 330; a second shield gas injection tube 340; a second source material gas injection tube 350; a third shield gas injection tube 360; and, a second oxidation gas injection tube 370.

[0038] The co-flow diffusion flame burner 300 according to the second preferred embodiment of the present invention is capable of forming uniformly thin layers over an area that is broader than the above-described co-flow diffusion flame burner 200 according to the first preferred embodiment of the present invention. This device further comprises a source material gas injection tube, two shield gas injection tubes, and an oxidation gas injection tube, in addition to the source material gas injection tube, the shield gas injection tube, and the oxidation gas injection tube.

[0039] With continued reference to FIG. 4, the first source material gas injection tube 310 is used for injecting a fuel gas g_(f), a source material S to be mixed with the fuel gas g_(f), and a dilution gas g_(d) to control the temperature of the flame, which is generated by the combustion of the fuel gas g_(f). The source materials may include SiCl₄, GeCl₄, POCl₃, BCl₃, and the like may be used. For the dilution gas, He, Ar, N₂, and other gas that can be diluted in hydrogen may be used.

[0040] The first shield gas injection tube 320 is disposed coaxially with the first source material gas injection tube 310 at the exterior of the first source material gas injection tube 310. This arrangement allows the injection of a shield gas g_(s) to prevent the particles produced by the combustion of the fuel gas g_(f), which is injected from the first source material gas injection tube 310, from sticking to the end of the injection tube 310. For the shield gas g_(s), a small amount of an inert gas may be used.

[0041] The first oxidation gas injection tube 330 is disposed coaxially with the first shield gas injection tube 320 at the exterior of the first shield gas injection tube 320. This arrangement allows the injection of an oxidation gas g_(o) to react with the fuel gas g_(f), which is injected from the first source material gas injection tube 310. Oxygen maybe used as the oxidation gas g_(o).

[0042] The second shield gas injection tube 340 is disposed coaxially with the first oxidation gas injection tube 330 at the exterior of the first oxidation gas injection tube 330. This is arrangement allows the injection of a shield gas g_(s) to prevent the particles produced by the combustion reaction of the oxidation gas g_(o), which is injected from the first oxidation gas injection tube 330, and the fuel gas g_(f), which is injected from the second source material gas injection tube 350, from sticking to the end of the injection tube 350.

[0043] The second source material gas injection tube 350 is disposed coaxially with the second shield gas injection tube 340 at the exterior of the second shield gas injection tube 340. The injection tube 350 is used for injecting a fuel gas g_(f), a source material S to be mixed with the fuel gas g_(f), and a dilution gas g_(d) to control the temperature of the flame, which is generated by the combustion of the fuel gas g_(f).

[0044] The third shield gas injection tube 360 is disposed coaxially with the second source material gas injection tube 350 at the exterior of the second source material gas injection tube 350. This arrangement allows the injection of a shield gas g_(s) to prevent particles produced by the combustion reaction of the fuel gas g_(f), which is injected from the second source material gas injection tube 350, and the oxidation gas g_(o), from sticking to the end of the injection tube 350.

[0045] The second oxidation gas injection tube 370 is disposed coaxially with the third shield gas injection tube 360 at the exterior of the third shield gas injection tube 360. This arrangement allows the injection of an oxidation gas g_(o) to react with the fuel gas g_(f), which is injected from the second source material gas injection tube 350.

[0046] The co-flow diffusion flame burner device 300 according to the second preferred embodiment of the present invention generates double flames, by which glass soot can be formed. Therefore, it is possible to deposit uniformly thin layers over a broader area.

[0047] Furthermore, by providing additional shield gas injection tubes, source material gas injection tubes, and oxidation gas injection tubes to the construction of the co-flow diffusion flame burner 300 according to the second preferred embodiment of the present invention, a co-flow diffusion multiple flames burner, that can generate multiple flames, can be obtained.

[0048] As described above, the co-flow diffusion flame burner according to the present invention can produce glass soot with a reduced particle size and uniform particle size distribution, thereby depositing the glass soot uniformly over a broader area.

[0049] While this invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiment; to the contrary, it is intended to cover various modifications within the spirit and scope of the appended claims. 

What is claimed is:
 1. A co-flow diffusion flame burner device for use in fabricating an optical waveguide comprising: a source material gas injection tube, through which a fuel gas, a source material to be mixed with the fuel gas, and a dilution gas to control the temperature of a flame generated by the combustion of the fuel gas are injected; a shield gas injection tube, disposed coaxially with the source material gas injection tube at the exterior of the source material gas injection tube and through which a shield gas is injected to prevent the particles produced by the combustion reaction of the fuel gas and an oxidation gas from sticking to the end of the source material gas injection tube; and, an oxidation gas injection tube, disposed coaxially with the shield gas injection tube at the exterior of the shield gas injection tube and through which an oxidation gas is injected to react with the fuel gas.
 2. The device according to claim 1, wherein the dilution gas comprises an inert gas.
 3. The device according to claim 1, wherein the shield gas comprises an inert gas.
 4. The device according to claim 1, wherein the source material is selected from the group consisting of SiCl₄, GeCl₄, POCl₃, and BCl₃.
 5. The device according to claim 1, wherein the dilution gas is selected from the group consisting of He, Ar, and N₂.
 6. A co-flow diffusion flame burner device for use in fabricating an optical waveguide comprising: a first source material gas injection tube through which a fuel gas, a source material to be mixed with the fuel gas, and a dilution gas to control the temperature of a flame generated by the combustion of the fuel gas are injected; a first shield gas injection tube, disposed coaxially with the first source material gas injection tube at the exterior of the first source material gas injection tube and through which a shield gas is injected to prevent the particles produced by the combustion of the fuel gas from sticking to the end of the first source material gas injection tube; a first oxidation gas injection tube, disposed coaxially with the first shield gas injection tube at the exterior of the first shield gas injection tube and through which an oxidation gas is injected to react with the fuel gas; a second shield gas injection tube, disposed coaxially with the first oxidation gas injection tube at the exterior of the first oxidation gas injection tube and through which a shield gas is injected to prevent the particles produced by the combustion reaction of the oxidation gas and the fuel gas from sticking to the end of the second shield gas injection tube; a second source material gas injection tube, disposed coaxially with the second shield gas injection tube at the exterior of the second shield gas injection tube and through which a fuel gas, a source material to be mixed with the fuel gas and a dilution gas to control the temperature of a flame generated by the combustion of the fuel gas are injected; a third shield gas injection tube, disposed coaxially with the second source material gas injection tube at the exterior of the second source material gas injection tube and through which a shield gas is injected to prevent particles produced by the combustion reaction of the fuel gas and the oxidation gas from sticking to the end of the second source material gas injection tube; and, a second oxidation gas injection tube, disposed coaxially with the third shield gas injection tube at the exterior of the third shield gas injection tube and through which an oxidation gas is injected to react with the fuel gas.
 7. The device according to claim 6, wherein the dilution gas comprises an inert gas.
 8. The device according to claim 6, wherein the shield gas comprises an inert gas.
 9. The device according to claim 6, wherein the source material is selected from the group consisting Of SiCl₄, GeCl₄, POCl₃, and BCl₃.
 10. The device according to claim 6, wherein the dilution gas is selected from the group consisting of He, Ar, and N₂.
 11. A process for fabricating an optical waveguide using a co-flow diffusion flame burner, the method comprising the steps of: introducing a fuel gas with a source material or a dilution gas into one end of the diffusion flame burner; introducing an oxidation gas into the one end of the diffusion flame burner; generating a flame at the one end of the diffusion flame burner where the fuel gas and the oxidation gas impinge; and, simultaneously introducing an inert gas to the one end of the diffusion flame burner to prevent the particles produced by the combustion of the fuel gas from sticking to the one end of the diffusion flame burner.
 12. The process according to claim 11, further comprising the step of bubbling the source material with the fuel gas or the dilution gas.
 13. The process according to claim 11, wherein the source material is selected from the group consisting of SiCl₄, GeCl₄, POCl₃, and BCl₃.
 14. The process according to claim 11, wherein the dilution gas is selected from the group consisting of He, Ar, and N₂. 